Riverside is a city in St. Clair County, Alabama, United States. It incorporated in 1886. At the 2010 census the population was 2,208, up from 1,564 in 2000.

St. Clair County is a county located in the central portion of the U.S. state of Alabama. As of the 2020 census, the population was 91,103. It has two county seats: Ashville and Pell City. It is one of two counties in Alabama, and one of 33 in the United States, with more than one county seat. Its name is in honor of General Arthur St. Clair, an officer in the French and Indian War. St. Clair County is included in the Birmingham, Alabama Metropolitan Statistical Area.